Greek officials initially said they had located pieces of plastic and two life jackets in the Mediterranean Sea, near where a transponder signal from the plane was emitted sometime before it fell off the radar. But that information turned out to be incorrect — Greek officials now say that nothing was found, and that the plane is still considered missing.

There were 66 people on board: 53 adults and three children, plus 10 crew members consisting of three security members, five cabin crew members, the pilot, and the copilot.

The flight took off from Paris' Charles de Gaulle Airport and was scheduled to land at Cairo Airport at 3:05 a.m. It lost contact with radar at 2:45 a.m. Cairo time (8:45 p.m. ET Wednesday), according to the airline.

The Airbus A320 had been traveling at 37,000 feet when it "swerved 90 degrees left, then 360 degrees right at 2:37 a.m. (Cairo time), while it was at 10-15 miles within Cairo's airspace at 37,000 feet," the Greek defense minister, Panos Kammenos, said in comments broadcast live on the state-run ERT TV. It then dropped to 10,000 feet and was lost from radar.

19PHOTOS

EgyptAir Flight Disappears (5/18)

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Wreckage from crashed EgyptAir flight MS804 has not been found, is still considered missing

A still image from video released May 19, 2016 shows EgyptAir Airbus A320 SU-GCC taking off at Brussels, Belgium, September 26, 2015. Mandatory credit The YottaTube/via REUTERS TV ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLY. NO RESALES. NO ARCHIVE. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THIS IMAGE.

An employee works at the EgyptAir desk at Charles de Gaulle airport, after an EgyptAir flight disappeared from radar during its flight from Paris to Cairo, in Paris, France, May 19, 2016. REUTERS/Christian Hartmann

An unidentified woman reacts as she waits outside the Egyptair in-flight service building, where relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo are being held, at Cairo International Airport, Egypt May 19, 2016. REUTERS/Amr Abdallah Dalsh

An unidentified man reacts as he waits outside the Egyptair in-flight service building, where relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo are being held, at Cairo International Airport, Egypt May 19, 2016. REUTERS/Mohamed Abd El Ghany

An unidentified woman reacts as she waits outside the Egyptair in-flight service building, where relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo are being held, at Cairo International Airport, Egypt May 19, 2016. REUTERS/Mohamed Abd El Ghany

The flight path of EgyptAir flight MS804 from Paris to Cairo is seen on a flight tracking screen May 19, 2016. Courtesy Flightradar24.com/Handout via Reuters

FILE PHOTO - An EgyptAir plane is seen on the runway at Cairo Airport, Egypt in this September 5, 2013 file photo. REUTERS/Mohamed Abd El Ghany/File Photo

Unidentified relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo react as they wait outside the Egyptair in-flight service building where relatives are being held at Cairo International Airport, Egypt May 19, 2016. REUTERS/Amr Abdallah Dalsh

FILE PHOTO - A general view shows the Terminal 1 at the Charles de Gaulle International Airport in Roissy, near Paris September 17, 2014, where missing EgyptAir flight MS804 originated from. REUTERS/Charles Platiau/File Photo

CAIRO, EGYPT - MAY 19: Relatives of passengers onboard missing EgyptAir flight MS804 cry at Cairo International Airport as they try to receive information in Cairo, Egypt on May 19, 2016. Airliner disappeared after entering the Egyptian airspace during its flight from Paris to Cairo.
(Photo by Ala Ahmed/Anadolu Agency/Getty Images)

French police officers and a sniffer dog patrol a terminal building at Charles de Gaulle airport, operated by Aeroports de Paris, in Roissy, France, on Thursday, May 19, 2016. Egypt deployed naval ships to search for an EgyptAir Airbus A320 en route to Cairo from Paris that went missing overnight off the coast of the North African country with 66 people on board. Photographer: Christophe Morin/Bloomberg via Getty Images

A screenshot from Flightradar24.com showing the flight track of EgyptAir flight MS804 from Paris, France, to Cairo, Egypt. The Airbus A320 with 66 people on board disappeared from radar on May 19, 2016. TASS (Photo by TASS\TASS via Getty Images)

Egypt's Aviation Minister Sherif Fathy speaks during a press conference on May 19, 2016 at the Ministry of Civil Aviation at Cairo's airport after an EgyptAir flight from Paris to Cairo crashed into the Mediterranean sea with 66 people on board.
The Airbus A320 fell 22,000 feet and swerved sharply twice in Egyptian airspace before it disappeared from radar screens, Greek Defence Minister Panos Kammenos told a news conference. Fathy said he could not rule out either terrorism or a technical problem.
/ AFP / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)

An employee sits at EgyptAir Airlines check in desk at Charles de Gaulle airport, operated by Aeroports de Paris, in Roissy, France, on Thursday, May 19, 2016. Egypt deployed naval ships to search for an EgyptAir Airbus A320 en route to Cairo from Paris that went missing overnight off the coast of the North African country with 66 people on board. Photographer: Christophe Morin/Bloomberg via Getty Images

CAIRO, EGYPT - MAY 19: Travelers come and go from terminal 3 at the Cairo International Airport on May 19, 2016 in Cairo, Egypt. EgyptAir flight MS804 from Paris to Cairo carrying 66 passengers and crew vanished over the eastern Mediterranean last night. (Photo by David Degner/Getty Images).

Unidentified relatives and friends of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo react as they wait outside the Egyptair in-flight service building where relatives are being held at Cairo International Airport, Egypt May 19, 2016. REUTERS/Amr Abdallah Dalsh

Egypt and EgyptAir flags are seen infront of an Egyptair in-flight service building, where relatives of passengers who were flying in an EgyptAir plane that vanished from radar en route from Paris to Cairo are being held, at Cairo International Airport, Egypt May 19, 2016. REUTERS/Amr Abdallah Dalsh

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US Secretary of State John Kerry said he had no special information about why the plane disappeared and added that he would not speculate on the cause.

"Relevant authorities are doing everything they can to try and find out what the facts are of what happened today," Kerry told a news conference at NATO headquarters in Brussels, Reuters reported.

Democratic presidential frontrunner and former Secretary of State Hillary Clinton told CNN's Chris Cuomo that it "does appear that it [the crash] was an act of terrorism."

Egypt and Greece have deployed military aircraft and a frigate to search the area, and a sea search is still underway. The French military says a Falcon surveillance jet monitoring the Mediterranean for migrants had been diverted to help the sea search.

Terrorism 'more likely' than technical failure

Egypt's aviation minister, Sherif Fathy, said in a news conference that an act of terror was more likely to be the cause of the crash than a technical failure.

US officials later told CNN that there are early indications a bomb took down the plane. Israeli officials have definitively ruled the crash a terror attack.

Still, some experts say there is nothing about the evidence so far that points directly to a terror attack.

"It could be a catastrophic mechanical malfunction, some kind of crew error, and so on," Patrick Smith, airline pilot and author of the book "Cockpit Confidential," told Business Insider on Thursday. "The plane's maneuvers by themselves don't indicate a whole lot. It's just too early to be speculating so broadly."

British pilot Alan Carter, who was flying a Boeing 747 in the same airspace at the same time as MS804, told the BBC conditions were "perfect" and "all air traffic communications were operating normal."

Greece's civil aviation department said that while it was in contact with the pilot, he seemed "in good spirits and thanked the controller in Greek," after he was cleared to exit the Greek airspace, according to Reuters. The pilot had logged more than 6,000 flying hours, EgyptAir said on Twitter.

Controllers apparently tried to contact the pilot 10 miles before the flight exited Greek airspace, but the pilot did not respond. Controllers continued trying to make contact until the plane disappeared from the radar but received no response.

"They did not radio for help or lose altitude," Ehab Mohy el-Deen, the head of Egypt's air navigation authority, told The New York Times. "They just vanished."

There are conflicting reports about whether an emergency signal was sent out before the plane crashed.

Troubled history

Flights over Egypt have encountered trouble on several occasions in the past year, prompting aviation authorities to instruct pilots to fly above 26,000 feet in the region.

The EgyptAir flight that disappeared on Thursday was delivered to EgyptAir in 2003 and had logged 48,000 flight hours, Airbus said in a statement on its Facebook page. The plane had engines made by the Swiss-based engine consortium IAE.

Airbus said it was ready to help authorities investigating the disappearance and said "our concerns go out to all those affected."

Smith, the pilot, was still reluctant to characterize EgyptAir as unsafe.

"EyptAir has what a lot of people would reasonably call a spotty safety record, but I'm a little uneasy saying that because, with crashes so few and far in between, all large commercial carriers are safe. In a more practical sense, I tend to doubt there's anything particular to EgyptAir that made this happen."